Figure 8-20: Earth-Size Exoplanets Kepler-20 is a star with five known exoplanets. The exoplanets Kepler-20e and Kepler-20f are illustrated in comparison to Earth and Venus. Kepler-20e (at 0.05 AU) has a radius just 0.87 times smaller than Earth, while Kepler-20f (at 0.1 AU) is 1.03 times larger than Earth. However, these objects orbit extremely close to their star and are much too hot for liquid water on their surfaces.

(Ames/JPL-Caltech/NASA)